Therein lies the crux of the issue. All new tenancies are subject to the new rules which allow rents to be charged up to 80% market value. If you move existing tenants, they then have a new tenancy.

Are you saying that all current tenancies are below 80% market value? We've had plenty of FMs, in other threads, state that they actually worked in HA, or for the council, and there was definitely, definitely no subsidy on social housing.

Mind, we've also had FMs who say that they're in social housing, and can't afford private rentals in their areas.